GA

COVID-19 Lecture Notes

COVID-19

Introduction

  • SARS-CoV-2 emerged in late 2019.
  • Caused a global pandemic.
  • COVID-19 clinical presentation ranges from asymptomatic to severe ARDS (Acute Respiratory Distress Syndrome).
  • WHO declared an end to the public health emergency in May 2023.

Virology and Variants

  • SARS-CoV-2 is a betacoronavirus.
  • It uses ACE2 for cell entry.
  • Variants like Alpha, Delta, and Omicron show different transmissibility and immune evasion.
  • Omicron sublineages dominate due to replication advantage in upper airways.

Epidemiology

  • High transmission occurs in congregate settings and among vulnerable populations.
  • Transitioning from pandemic to endemic status.
  • Over 15 million excess deaths estimated in 2020–2021.

Clinical Spectrum of COVID-19

  • Ranges from asymptomatic to critical illness.
  • 20–40% of infections are asymptomatic.
  • Omicron variants generally associated with milder illness.

Common Symptoms

  • Initial symptoms: nasal congestion, cough, sore throat, fatigue.
  • Fever is not always present at onset.
  • Gastrointestinal (GI) symptoms in approximately 18%: diarrhea, nausea, abdominal pain.

Clinical Classifications

  • Mild: No hypoxia or abnormal chest imaging.
  • Moderate: Lower respiratory symptoms, SpO_2 \geq 94\%. (This indicates the patient's oxygen saturation is greater than or equal to 94%)
  • Severe: SpO_2 < 94\%, >50% lung involvement, tachypnea. (This indicates the patient's oxygen saturation is less than 94% and there is more than 50% lung involvement.)
  • Critical: Respiratory failure, septic shock, or multiorgan dysfunction.

Risk Factors for Severe Illness

  • Advanced age (especially \geq 65 years).
  • Immunocompromised states, comorbidities (e.g., diabetes, heart disease).
  • High viral load, lack of antibody response.

Complications

  • ARDS is the major complication in severe cases.
  • Cardiac issues: arrhythmias, myocarditis, shock.
  • Thrombosis: DVT (deep vein thrombosis), PE (pulmonary embolism), stroke, arterial events.

Long COVID and Sequelae

  • Persistent symptoms >4 weeks after infection.
  • Common symptoms: fatigue, dyspnea, memory problems.
  • Can involve respiratory, cardiovascular, neurologic systems.

Special Populations

  • Children: typically mild, risk of MIS-C (Multisystem Inflammatory Syndrome in Children).
  • Pregnant women: same approach as nonpregnant individuals.
  • HIV patients: similar presentation, higher risk of severe outcomes.

Diagnosis of COVID-19

  • Clinical suspicion based on respiratory and systemic symptoms.
  • NAAT (RT-PCR) preferred for diagnosis due to high sensitivity.
  • Antigen tests useful for rapid testing, especially in community settings.

Testing Indications

  • Test symptomatic individuals with implications for treatment or infection control.
  • Test selected asymptomatic individuals after known exposure.
  • Serial testing useful in outbreak and congregate settings.

Outpatient Management

  • Stratify patients by severity: mild, moderate, or severe.
  • Mild cases managed via telehealth with symptom monitoring.
  • Moderate to severe cases may need in-person or emergency care.

Therapeutics

  • Initiate treatment early in high-risk outpatients.
  • Options include antivirals like nirmatrelvir/ritonavir (Paxlovid), remdesivir.
  • Monoclonal antibodies are less used due to variant resistance.

Vaccines: Overview

  • Vaccines are key to reducing severe disease and mortality.
  • mRNA (Moderna, Pfizer) and protein-based (Novavax) vaccines are used.
  • Current formulations target Omicron variants.

Vaccine Recommendations

  • CDC recommends vaccination for all individuals \geq 6 months.
  • High-priority groups: elderly, immunocompromised, comorbid conditions.
  • Boosters updated for circulating variants (e.g., KP.2 in 2025).

Conclusion

  • COVID-19 remains a critical health issue despite lower mortality.
  • Vaccination, early diagnosis, and outpatient triage are central to management.
  • Continuous surveillance and variant adaptation remain vital.